The present invention generally relates to environmental control systems and, more specifically, to a multi-stage catalytic control system and method for providing a supply of breathable air under conditions where chemical and biological toxic compounds may be present in the ambient air.
In certain applications, it may be highly desirable to remove chemical and biological toxic compounds from the air. Catalysts may be used to destroy certain toxic compounds in an air stream. In order for air to be breathable, by-products of the destruction of toxic compounds must be removed. For example, nitrogen oxides (NOx) produced from the destruction of nitrogen containing compounds must be removed, typically through the use of a NOx post-treatment filter (PTF). Conventional methods heat the air to a high temperature, typically about 300° C., that is provided to the catalyst. This high temperature oxidation of the ambient air may result in a high percentage of the nitrogen containing compounds to be oxidized into NOx. As a result, either large PTF assemblies are required or PTF assemblies need to be replaced often, to adequately remove toxins from an air stream in order to produce breathable air.
A Catalytic Oxidation (CATOX) system 10 in the prior art technology is shown in FIG. 1. Referring to FIG. 1, CATOX System 10 consists of individualized elements. Ambient air may be supplied to a lower temperature heat exchanger or recuperator 12 via a line 14. The lower temperature heat exchanger 12 may be used to heat the incoming ambient air through line 14 with energy in the treated air exiting the post treatment filter 22. High temperature blower 16 moves the ambient air through line 14, low temperature heat exchanger 12 and into heater 18. Heater 18 further heats the ambient air to about 300° C. and is then introduced into an oxidation catalyst 20 where certain toxic compounds may be oxidized. The effluent from the catalytic oxidation catalyst 20 is then passed through post treatment filter 22 where some un-oxidizizable compounds in the ambient air and acid gases or NOx, produced in the oxidation catalyst 20, may be destroyed or removed. The treated ambient air exiting post treatment filter 22 may then be passed through the hot side of low temperature heat exchanger 12 to preheat the ambient air entering through line 14.
As can be seen, there is a need for an apparatus and methods for the destruction of chemical and biological impurities from an air stream to yield a source of breathable air. Furthermore, there is a need for such an apparatus to oxidize nitrogen containing compounds while reducing the production of NOx and a need for such an apparatus to be suitable for mobile platforms.